Method of treating paper



Patented Apr. 7, I925.

, UNHTED STATES TENT @FFIQE.

METHOD OF TREATING PAPER.

NO Drawing,

To all whom it may concern:

Be it known that I, Jonson A. DE Cnw, a citizen of Canada, residing at Mount Vernon, New York, have invented certain new and useful Improvements in Methods of Treating Paper, of which the following is a specification.

This invention relates to a new process for treating paper making fibres for the pur ose of chan in the h sical character- P 2: s P y of the fibrous material and rendering it more suitable for high speed machines such as are used in the manufacture of newsprint paper.

In the manufacture of newsprint and similar papers in which no rosin size is used, it is still found necessary to use an astringent such as sulphate-of alumina, not for the purpose of coagulating sizing material, but for the purpose of rendering the fibres more astringent so that they will not stick to the presses and cause breaks on the machine when running at high speed.

Sulphate of alumina is used in the manufacture of newsprint paper in the approximate proportions of one part of sulphate of alumina to one hundred parts of paper fibre. As the paper stock passes on the machine, however, it is diluted with water proportions of about one part of fibre to about two hundred parts of water, the alum, therefore, will be diluted in the proportions of one part of sulphate of alumina to twenty thousand parts of water. At such a' dilution, the sulphate of alumina will be largely decomposed so that the most of the alumina will be taken up by the fibres by absorption and some of the sulphuricacid is also taken into the fibre but the water runningaway from the machine contains free sulphuric acid, which will have a tendency to corrode all piping and metallic parts with which itcomes in contact, especially when 1t is used over and over again in the process of manufacture, in which case, the amount of acidity will increase up to a certain point a 'of stability depending upon the amount of fresh water used. I

In practice, it is fully recognized that the use of sulphate of alumina in a newsprintpaper-mill is a constant source of corrosion and wear and tear, both as regards machine piping and also the wires and cotton felts of the paper machine.

Up to the present time, no other material in the Application filed June 19, 1923. Serial No. 646,480.

than sulphate of alumina has been found to give the same results, so that the corrosive effect of the alum in these mills is tolerated in order to get machine production.

I have discovered, however, a substitute for sulphate of alumina in this process which will not only have the same similar astringent effects upon the fibres which prevent their sticking to the presses, but it is a chemical and a stronger base and when in solution will not decompose as much as sulphate of alumina and consequently does not produce the free acid which causes corrosion.

The chemical material is not one of the usual soluble salts known to the trade but is material which is known in the trade as an insoluble filling material and is used, at the present time, solely for the purpose of loading papers in order to increase their weight.

The reason it has never been used knowingly in the solution form as an alum substitute is because it is very slightly soluble, its saturated solution containing only two parts per one thousand of water. This material is the well known filling material, calcium sulphate, (CaSQ It would be possible therefore, to dissolve forty pounds of this material in twenty thousand pounds of water so that its solubility is moderately in excess of the amount necessary of its use as a substitute for sulphate of alumina.

My method of using this material is to mix ground or preciptated calcium sulphate with the largest amount of water that can be conveniently vadded to the paper stock, orit may be added directly, into the heaters or mixing chest.

The process is preferably carriedin such a manner that when the diluted paper stock passes on the wire it'would contain in solu- I twenty parts of caltion, approximately ten thousand of fibrous cium sulphate to one material.

It is not desirable to obtain a supersaturated solution but merely a solution which willact almost in the same way as sulphate of alumina because the fibres will take up a portion of this salt by adsorption which preventstheir sticking to the presses and thus all the technical advantages obtained from sulphate of alumina are duplicated.

This salt, however, does not produce acidity in the solution and consequently there will be no corrosive effect upon any part of the machine or the machine clothing.

This material also had a tendency to harden the pitohy material sometimes found in ground Wood and sulphite pulp. It apparently forms a calcium resinate over the surface of the pitch.

Up to the present time, the slight amount of solubility of calcium sulphate has been the chief objection to its use as a filling material and no one has ever claimed that the solution of calcium sulphate could be used to any advantage in paper making.

I therefore claim as my invention: The process of treatlng paper-making 15 fibres to be used in a slack sized paper, to render them more astringent, which consists in bringing them into contact before or during the paper-makingprocess with an aqueous solution of calcium sulphate in 20 Which there is more calcium sulphate than in natural mill Water, but not enough to act as afiller for the paper.

In testimony whereof I have affixed my signature to this specification.

JUDSON A. DE CIGW. up 

